Various lesions are treated in the oral maxillofacial regions such as jaw cysts, benign and malignant tumours, mucous diseases, maxillofacial fractures, congenital discorders of cleft lip and palate, facial deformities and temporo-mandibular disorders. The large amount of data which includes X-ray, computed tomogram (CT), magnetic resonance image (MRI) and so on, has been accumulated to diagnose and follow up for prognosis of patients. It is impnd and urgent not only for clinical studies and education, but also for patients to make the best use of important and multiple information and feed back clinically.With the dedatabase system for dento-facial deformities, contributing factors to postoperative relapse in simultaneous surgery of maxilla and mandible were investigated by a multiple stpwise regression analysis. Cephalograms were randomly traced and measured in the radiographic landmarks to obtain a consistent sell-nasion. The landmark points and angles were as follows : 1. Point A ;
… More horizontal distance AX and vertical distance AY,Point B ; horizontal distance BX and vertical distance BY,U1 : U1.X and U1Y,L1 ; L1X and L1Y,Pogonion ; Pog.X and Pog.Y,SNA,SNB,P P and M P.Results.The average postsurgical change is 4.5mm in vertical advancement of point A (Apoint.X), and 11.4mm in vertical setback of Pogonion (Pog.X).At 1 year postsurgery, point A has the tendency to upward movement, while the change degree at point B and Pogonion are larger than that of point A.From these mesurements and statistical data with cephalogram, main contributing factor to point A relapse after surgery was investigated by multiple stepwise regression analysis. As the many variables, predictable factors were assessed acording to the degrees of partial correlation and simple correlation. The main factors to influence on relapse at point A result in the vertical and horizontal movement at L1 and Pogonion, also angle change at mandibular plane at surgery. Otherhand, postsurgical vertical and horizontal movements at point B cause unstability at surgical site of maxilla. Less